Fluid spring tensile energy accumulator and shock absorbing device for well pipe strings



Nov. 21, 1967 H. w. HARRISON 3,353,613

FLUID SPRING TENSILE ENERGY ACCUMULATOR AND SHOCK ABSORBING DEVI FOR WELL PIPE STRINGS Filed pt. 24, 1965 INVENTOR 1 /4812) 14/. flmeexspn/ United States Patent 3,353,613 FLUID SPRING TENSILE ENERGY ACCUMULA- TOR AND Si-IQCK ABSQRBING DEVICE FOR WELL PIPE TRINGS Harry W. Harrison, Houston, Tex., assignor to Houston Engineers, Inc., Houston, Tern, a corporation of Texas Filed Sept. 24, N65, Ser. No. 489,936 9 Claims. (Cl. 175-293) ABSTRACT OF THE DISCLOSURE A fluid spring tensile energy accumulator and shock absorbing device designed to provide a closed chamber to increase the effect of the jarring tool associated therewith while at the same time absorbing the shock caused by operation of such tool with the design of the device being further characterized by the positive prevention of vacuum formation in the chamber, thereby increasing the efiiciency of the device.

This invention is an improvement over that disclosed and claimed in Patent 2,953,352 of D. D. Webb issued Sept. 20, 1960, and this invention relates particularly to a device to be connected in a well pipe string to accumulate or store tensile energy and to absorb shock occasioned by operation of a jarring tool normally utilized to free pipe or well tools which have become wedged or stuck in the well.

In the drilling of oil or other wells which frequently go to a great depth in the earth, the drilling tools are attached to the lower end of a pipe string which is lowered within the well and provides the driving connection for the drilling tools. Occasionally either the tools or the pipe become jammed or wedged in the well and it is sometimes exceedingly difiicult to remove such parts from the well in order to repair the same and resume drilling operations. Where a direct pull from the surface is insuflicient to dislodge the stuck parts it has been customary to utilize what is commonly known as a jarring tool which in effect provides a sucession of hammer blows in an axial direction to free parts and permit withdrawal of the same from the well.

The jarring tool is normally interposed in the pipe string relatively close to the drilling tools and, in operation, when it is desired to remove parts which have become jammed in the well bore, a strong upward force is applied to the pipe string actuating the jarring tool to impart hammer blows to free the stuck parts and permit withdrawal of the same from the well bore. The operation of the jarring tool imparts extremely high impact loads or shocks to the well string as well as to the jammed tool or other part wedged in the well and also to the hoisting equipment at the surface. Such shock materially reduces the life of the well equipment and also reduces the eifec-tiveness of the jarring operation. It has also been found that the eliectiveness of conventional jarring tools is materially reduced when such tools are utilized in a well bore which is crooked or has been drilled at an angle to the vertical since the resiliency of the pipe string is absorbed into the well bore wall; hence the jarring effect is dampened.

While the device disclosed in the above identified Webb patent is effective in operation and materially increases the efiiciency of jarring tools while reducing the shock applied to the well string and hoisting equipment, nevertheless this device during operation produces a vacuum in the lower part of the fluid chamber below the piston and as a consequence thereof there is a relatively great surge load on the packing means at the opposite ends of the chamber as a result of which more costly and compk): packing means must be utilized and, furthermore, the danger of leakage at these points is increased.

It is accordingly an object of the invention to provide a combined tensile energy accumulator and shock absorbing device which may be conveniently installed in well pipe strings without requiring any modification whatsoever and which operates to materially increase the efiiciency of jarring tools also installed in the pipe string.

A further object of the invention is the provision of a combined tensile energy accumulator and shock absorbing device for well pipe strings which operates to store tensile energy and release the same on the actuation of a jarring tool and at the same time operates to absorb shock caused by operation of such jarring tool.

A still further object of the invention is the provision of a combined tensile energy accumulator and shock absorbing device for well strings which may be installed in the string adjacent a jarring tool and in which relative movement caused by operation of the jarring tool is substantially confined to the section between the upper end of the tensile energy accumulator and shock absorbing device and the tool or other object to be removed from the well thereby maintaining the efficiency of the jarring device and preventing absorption of the force exerted thereby by the pipe string disposed in a well having a crooked bore or one drilled at angle to the vertical.

Another object of the invention is the provision of a tensile energy accumulator and shock absorbing device for well pipe strings which may be conveniently installed in such pipe string and which will in no way interfere with normal drilling operations.

A further object of the invention is the provision of a combined tensile energy accumulator and shock absorbing device for well pipe strings and including a chamber completely filled with a compressible fluid which during operation of the device is compressed in a manner to preclude the presence of a vacuum in any portion of the chamber.

A still further object of the invention is the provision of a combined tensile energy accumulator and shock absorbing device for well pipe strings which may be conveniently and economically manufactured from readily available materials and which may be conveniently utilized with conventional jarring tools and other well equipment.

Further objects and advantages of the invention will be apparent from the following description taken in conjunction with the accompanying drawing wherein:

FIGURE 1a is a longitudinal sectional view of the upper half of a tensile energy accumulator and shock absorbing device constructed in accordance with this invention;

FIGURE 1b is a longitudinal sectional view showing the lower half of the tool shown in FIGURE 11:;

FIGURE 2 is a sectional view taken substantially on the line 2-2 of FIGURE la;

FIGURE 3 is a sectional view taken substantially on the line 3-3 of FIGURE lb; and

FIGURE 4 is a sectional view taken substantially on the line 44 of FIGURE 1b.

With continued reference to the drawing there is shown a combined tensile energy accumulator and shock absorbing device for well pipe strings constructed in accordance with this invention and which may well comprise an elongated tubular body 10 having an upper section 11, a central section 12 and a lower section 13. The upper section 11 is detachably secured to the central section 12 by a suitable screw-threaded joint 14 and the central section 12 is detachably secured to the lower section 13 by a suitable screw-threaded joint 15.

A one piece hollow mandrel 16 is slidably received within the body 10 and extends from above the upper section 11 into the lower section 13. Detachably secured to the upper end of the mandrel by a suitable screw threaded joint 17 is a coupling member 18 for detachably connecting the device of this invention to the lower end of a well pipe string. The mandrel 16 is provided intermediate the length thereof with a plurality of angularly faced external ribs 19 which are slidably received in angularly spaced internal grooves '20 in the central section 12 and which serves to provide a splined connection between the mandrel 16 and the body in order to prevent relative rotation therebetween and permit the transmission of torque from the well pipe string through the body 10 to a tool or other element secured to the lower end thereof in a manner to be later described. As will be noted from an inspection of FIGURE 2 the central section 12 is provided with additional internal axially extending grooves 21 and the purpose of such grooves will also be later described.

The portion 22 of the mandrel 16 above the upper end of the ribs 19 is smooth and is of appreciably less diameter than the inner diameter of the upper section 11 of the body 10. Provided in the upper end of the upper section 11 is a suitable fluid tight packing means 23 which serves to engage the outer surface of the upper portion 22 of the mandrel 16 to provide a fluid tight engagement therebetween. Also provided at the upper end of the upper section 11 is a suitable wiper means 24 engaging the surface of the mandrel to prevent the entry of foreign material into the packing means 23 which operates to prolong the life thereof.

Somewhat below the lower ends of the ribs 19 on the mandrel 16 there is provided an upwardly facing shoulder 25 and below such shoulder 25 the lower portion 26 of the mandrel 16 is smooth and is of somewhat greater diameter than the upper portion 22 of the mandrel above the ribs 19. A suitable fluid tight packing means 27 is provided adjacent the lower end of the central section 12 and such packing means 27 engages the lower portion 26 of the mandrel 16 to provide a fluid tight engagement therebetween. Conveniently the packing means 27 may be secured in place by means of the screw threaded joint between the central section 12 and the lower section 13 of the body 10.

The space between the lower packing means 27 and the upper packing means 23 and between the outer surface of the mandrel 16 and the inner surfaces of the upper section 11 and central section 12 serves to provide a chamber 28 which is completely filled with a compressible fluid and such fluid may be introduced through a filling opening 29 in the lower portion of the central section 12 and such opening 29 may be closed by a removable screw threaded plug 30. In order to provide for complete filling of the chamber 28 with the compressible fluid there may be provided adjacent the upper end thereof in the upper section 11 a vent opening 31 closed by a removable screw threaded plug 32. Suitable compressible fluids for filling the chamber 28 are commercially available.

The lower end of the lower section 13 of the body 10 is provided with a suitable screw threaded coupling means 33 which may be utilized to detachably connect the body 10 to a jarring tool or other elements such as a well pipe or a drilling tool.

In operation when it is desired to exert an upward force on a jarring tool to remove an object jammed or stuck in a well it is only necessary to apply an upward force to the upward coupling member 18 which serves to move the mandrel 16 upwardly within the body 10 and such upward movement of the mandrel 16 will cause the lower portion 26 of the mandrel 16 below the shoulder 25 to move upwardly into the chamber 28 thereby reducing the volume of such chamber and compressing the fluid contained therein. This compression of the fluid in the chamber 28 will be accomplished without in any way producing a vacuum at any point in the chamber 28 since there is no separate piston which moves upwardly within the cylinder leaving a void beneath the same as in the Webb patent identified above and consequently the total upward force will be expended in compressing the fluid in the chamber 28 and none of this force will be expended in creating a vacuum in such chamber. Upon completing the application of the desired upward force the jarring tool may be actuated and at this time the body 10 will move upward suddenly thereby releasing the energy stored in the compressed fluid 28 to the jarring tool and at the same time providing a cushion against the shock occasioned by the actuation of the jarring tool and consequently such shock will be substantially confined to the portion of the apparatus below the device of this invention and furthermore substantially the entire upward force exerted from the surface of the well will be applied to the jarring tool since such energy is stored in the device of this invention and is not dissipated in the portion of the well string above the device of this invention. As a result the efficiency of the jarring tool is maintained at a maximum and at the same time damage to the well string or hoisting equipment is substantially eliminated by reason of the shock absorbing characteristics of the device of this invention.

It will be obvious to those skilled in the art that various changes may be made in the invention without departing from the spirit and scope thereof and therefore the invention is not limited by that which is shown in the drawings and described in the specification but only as indicated in the appended claims.

What is claimed is:

1. A combined tensile energy accumulator and shock absorbing device for well pipe strings, said device comprising an elongated tubular body having an upper section, a central section and a lower section, said sections being detachably secured together, a one piece hollow mandrel slidably received in said sections, interengaging splines on said mandrel and said central section to prevent relative rotation between said mandrel and said body, the outer surface of said mandrel above said splines being smooth and of less diameter than the inner diameter of said upper section, a shoulder on said mandrel below said splines, the outer surface of said mandrel below said shoulder being smooth and of greater diameter than the diameter of said mandrel above said splines, fluid tight packing means adjacent the upper end of said upper section engaging said mandrel above said splines, fluid tight packing means adjacent the lower end of said central section engaging said mandrel below said shoulder, the space between said packing means and between the outer surface of said mandrel and the inner surfaces of said upper and central sections providing a closed chamber, a compressible fluid completely filling said chamber, means on the upper end of said mandrel for detachably connecting a well pipe string, and means on the lower end of said lower section for detachably connecting a jarring tool, whereby upon exerting an upward force on said mandrel the same will move upwardly with respect to said body with the lower large diameter portion of said mandrel moving upwardly in said chamber to reduce the volume and compress said fluid While precluding the presence of a vacuum in any portion of said chamber and impose an upward force on said jarring tool and upon actuation of said jarring tool said body will move upwardly relative to said mandrel to expend the energy stored in the compressed fluid and absorb shock caused by said jarring tool.

2. A device as defined in claim 1 in which wiping means is provided adjacent the upper end of said upper section engaging said mandrel to prevent entry of foreign material to the packing means at the upper end of said upper section.

3. A device as defined in claim 1 in which filling means is provided adjacent the lower end of said chamber and venting means is provided adjacent the upper end thereof.

4. A device as defined in claim 1 in which additional longitudinal grooves are provided in the inner wall of the splined portion of said central section to increase the volume of said chamber and to provide free communication between opposite ends of the splined portion.

5. A device as defined in claim 1 in which the packing means adjacent the lower end of said central section is secured in place by the detachable joint between said central section and said lower section.

6. A combined tensile energy accumulator and shock absorbing device for well pipe strings, said device comprising an elongated tubular body having an upper section, a central section and a lower section, said sections being detachably secured together, a mandrel slidably received in said sections, interengaging splines on said mandrel and said central section to prevent relative rotation between said mandrel and said body, the outer surface of said mandrel above said splines being of less diameter than the inner diameter of said upper section, a shoulder on said mandrel below said splines, the outer surface of said mandrel below said shoulder being of greater diameter than the diameter of said mandrel above said splines, fluid tight packing means adjacent the upper end of said upper section engaging said mandrel above said splines, fluid tight packing means adjacent the lower end of said central section engaging said mandrel below said shoulder, the space between said packing means and between the outer surface of said mandrel and the inner surfaces of said upper and central sections providing a closed chamber, a compressible fluid filling said chamber, means on the upper end of said mandrel for detachably connecting a well pipe string, and means on the lower end of said lower section for detachably connecting a jarring tool, whereby upon exerting an upward force on said mandrel the same will move upwardly with respect to said body with the lower large diameter portion of said mandrel moving upwardly in said chamber to reduce the volume and compress said fluid while precluding the presence of a vacuum in any portion of said chamber and impose an upward force on said jarring tool and upon actuation of said jarring tool said body will move upwardly relative to said mandrel to expend the energy stored in the compressed fluid and absorb shock caused by said jarring tool.

7. A combined tensile energy accumulator and shock absorbing device for well strings, said device comprising an elongated tubular body, means formed at one end of said body for detachably connecting a jarring tool, a mandrel slidably received in said body, means on said mandrel for detachably connecting a well pipe string, said mandrel being formed exteriorly so as to provide a small diameter portion radially spaced throughout its length from the portion of said body disposed circumferentially therearound, and a larger diameter portion spaced close to but in non-fluid tight relation with the portion of said housing disposed circumferentially therearound, first packing means disposed within said body adjacent said small diameter portion of said mandrel, second packing means disposed within said body adjacent said larger diameter portion of said mandrel, said packing means, said body, and the exterior of said mandrel defining a closed, fluid tight chamber, the space below said second packing means freely communicating with said one end of said body, a compressible medium in said chamber, movement of said mandrel in one direction relative to said body eflecting movement of said relatively large diameter portion of said mandrel into said closed fluid tight chamber to compress said compressible medium without formation of a vacuum therebelow thereby imposing a force in such direction on said jarring tool, subsequent actuation of the latter causing movement of said body relative to said mandrel to expend the stored energy and absorb shock caused by said jarring tool.

8. The device of claim 7 further including interengaging splines formed on said mandrel and said housing to permit relative axial movement but prevent relative rotative movement therebetween.

9. The device of claim 8 wherein said mandrel is formed with radially extending, arcuately spaced ribs which form said spline connection, said ribs being of a diameter at the outer peripheries thereof equal to diam eter of said relatively large diameter portion of said mandrel and extending longitudinally upwardly therefrom.

References Cited UNITED STATES PATENTS 2,544,473 3/1951 Smith l296 2,671,640 3/1954 Baker -294 2,953,352 9/1960 Webb 6423 3,230,740 1/1966 Fox 64-23 JAMES A. LEPPINK, Primary Examiner. 

7. A COMBINED TENSILE ENERGY ACCUMULATOR AND SHOCK ABSORBING DEVICE FOR WELL STRINGS, SAID DEVICE COMPRISING AN ELONGATED TUBULAR BODY, MEANS FORMED AT ONE END OF SAID BODY FOR DETACHABLY CONNECTIN A JARRING TOOL, A MANDREL SLIDABLY RECEIVED IN SAID BODY, MEANS ON SAID MANDREL FOR DETACHABLY CONNECTING A WELL PIPE STRING, SAID MANDREL BEING FORMED EXTERIORLY SO AS TO PROVIDE A SMALL DIAMETER PORTION RADIALLY SPACED THROUGHOUT ITS LENGTH FROM THE PORTION OF SAID BODY DISPOSED CIRCUMFERENTIALLY THEREAROUND, AND A LARGER DIAMETER PORTION SPACED CLOSE TO BUT IN NON-FLUID TIGHT RELATION WITH THE PORTION OF SAID HOUSING DISPOSED CIRCUMFERENTIALLY THEREAROUND, FIRST PACKING MEANS DISPOSED WITHIN SAID BODY ADJACENT SAID SMALL DIAMETER PORTION OF SAID MANDREL, SECOND PACKING MEANS DISPOSED WITHIN SAID BODY ADJACENT SAID LARGER DIAMETER PORTION OF SAID MANDREL, SAID PACKING MEANS, SAID BODY, AND THE EXTERIOR OF SAID MANDREL DEFINING A CLOSED, FLUID TIGHT 